JPH05127550A - Heating device - Google Patents

Abstract

PURPOSE:To eliminate the shortage of heating at an end part caused by heat radiation at the end part of a thermal heater by making the adiabatic effect by a heat insulating member larger at the end part than at a central part. CONSTITUTION:This device is provided with a heating body arranged along a direction crossed with the moving direction of a recording material and a heat insulating holder 1 which adiabatically supports the heating body along a longitudinal direction. Then, the holder 1 is provided with a U-shaped recess 6 which forms space with the heating body at the end part of the holder 1. The adiabatic effect by the holder 1 is larger at the end part than at the central part, and heat radiation from both ends of the heating body to the holder 1 becomes smaller than that at another part, thereby softening the temperature effect at the end part on the surface of a body to be heated. Since the adiabatic effect by the holder 1 is made larger at the end part, the escape of the heat toward the end part is compensated, and the part to be heated corresponding to the end part of the heating body is fully heated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for heating an image on a recording material with heat from a heating body which is heat-insulated and supported by a heat insulating holder.

In particular, the present invention relates to a heating device suitable for use as a fixing device for heating and fixing an unfixed image in an image forming device such as an electrophotographic device or an electrostatic recording device.

It can also be used as an apparatus for modifying the surface property of an image.

[0004]

2. Description of the Related Art Conventionally, for example, a recording material heating apparatus for heating and fixing an image includes a heating roller which is maintained at a predetermined temperature and a pressure roller which has an elastic layer and presses against the heating roller. A heat roller method is widely used in which a recording material is nipped and conveyed while being heated.

However, the heat roller fixing method has a problem that it requires a long warm-up time until the surface of the heat roller reaches the fixing temperature.

[0006] Therefore, the applicant of the present invention, JP-A-2-134667, JP-A-2-154284, JP-A-2-15
No. 4,285, JP-A-2-157878, and the like, a thermal fixing device using a thermal heater fixedly supported and a thin film that slides on the heater is proposed.

In such a heating device, since the heater is adiabatically supported by the adiabatic holder and the heat is concentrated on the image side, the heat efficiency is high, and since the heater having an extremely low heat capacity can be used, the warm-up time is large. It can be shortened.

[0008]

However, in the above film heating device, since the heat capacity of the heating body is small, the temperature drop at the end portion in the longitudinal direction of the heating body becomes large due to the heat radiation toward the end portion. The heating of the heated material portion corresponding to the end portion of the body becomes insufficient, and in the case of the image fixing device, the problem that the fixing property of the image deteriorates only in that portion occurs.

To solve this problem, it is conceivable to make the heating body length sufficiently large with respect to the maximum image area, but the apparatus becomes large.

[0010]

SUMMARY OF THE INVENTION According to the present invention, which solves the above-mentioned problems, a heating body is provided along a direction intersecting the moving direction of a recording material, and the heating body is thermally insulated and supported along the longitudinal direction. In a heating device having a heat insulating holder, the heat insulating effect of the heat insulating member is enhanced in the end portion rather than the central portion.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a heat fixing device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 designates a holder for heat-insulating and supporting a heating body 2 described later, which is made of a heat-resistant resin.

This heat insulating holder is an endless film 7
It also serves as a guide for guiding the inner surface of the device and a stay as a reinforcing member of the device.

The heating element 2 is provided so that the longitudinal direction thereof intersects with the moving direction of the fixing film 7, in particular, the direction orthogonal thereto.

The heating element 2 is composed of a heater substrate 3 made of alumina, which is a ceramic having good thermal conductivity, and an electric resistance material such as Ag / Pd (silver palladium) along the substantially central portion of the lower surface of the heater substrate 3 on the film side. Thickness about 10 μm, width 1-3
mm has a resistance heating element 4 coated by screen printing or the like, and has a glass protective layer for insulation and protection on the resistance heating element 4.

Furthermore, in order to reduce friction with the fixing film 7, PFA. You may coat fluororesins, such as PTFE.

The heater substrate 3 is integrally attached and supported on the lower surface side of the heat insulating holder along the length of the lower surface.

7 is an endless heat resistant film,
The stay 1 including the heating element 2 is externally fitted. The inner peripheral length of the endless heat-resistant film 7 and the outer peripheral length of the holder 1 including the heating element 5 are larger than those of the film 7 by, for example, 3 mm, and therefore the film 7 is larger than the holder 1 including the heating element 2. The circumference is fitted loosely with a margin. The film 7 has a total thickness of 10 in order to reduce the heat capacity and improve the quick start property.
A single layer or a composite layer film having a heat resistance, a mold releasability, strength, durability, etc. of 0 μm or less, preferably 40 μm or less and 20 μm or more can be used.

Reference numeral 8 denotes a pressure roller as a rotating body which forms a nip by sandwiching the film 7 with the heating body 2, and has a central shaft 9 and a rubber having a good releasability such as a silicone rubber which is sheathed on the shaft. The roller portion 10 is made of an elastic body, and the left and right ends of the central shaft 9 are rotatably supported by bearing members (not shown).

The pressure roller 8 is driven by a drive source (not shown), and the film 7 is rotated by the pressure roller 8.

FIG. 2 shows a perspective view of the heat insulation holder.

In the present embodiment, the length in the longitudinal direction of the resistance heating element is set to be substantially the same as the maximum image area, and the heat insulating holder which is a supporting / reinforcing member for the heating element 5 is shown in FIG. 2 where the end of the resistance heating element corresponds
~ 3mm width 4.5mm from outside position, length 20mm,
A boat-shaped recess 6 having a depth of 2 mm is provided.

Due to the recess 6, a gap exists between the heater substrate 3 and the heat insulating holder 1 at the longitudinal end of the heating element.

The heat insulating effect of this heat insulating holder becomes larger at the end portion than at the central portion, and the heat radiated from both end portions of the heating body to the heat insulating holder is smaller than at other portions, and the temperature drop at the end portion on the surface of the heated body is reduced. To be done. According to an experiment conducted by the inventors, when a stay having no depression is used as shown in FIG. 5, the temperature of the end of the image area of the heated object is lower than the fixing control temperature by 30d.
eg. Although it may have dropped by more than the above, in the experiment using the stay provided with the recess 6, the temperature drop was 10 de
g. It became within. Thus, the temperature drop at the end in the longitudinal direction is 10 deg. Within the range, the pressure is applied from both ends of the central axis 9 of the pressure roller, which is compensated for by the pressure applied at both ends being slightly higher than the central portion, and uniform and good fixing property can be obtained over the entire image width. .

Next, FIG. 3 shows a longitudinal relationship diagram of this apparatus.
As shown in FIG. 3, unless the length of the resistance heating element is equal to or longer than the maximum image area, it is difficult to obtain good fixability over the entire image area. Further, since the outside of the dent is substantially the same as or outside the end of the resistance heating element, heat escaping outward from the end of the heating element can be prevented, and the effect of the present invention works more effectively with a small dent. Further, making the length of the heating element 2 longer than the outside of the depression has the advantages of facilitating attachment and facilitating mechanical strength.

(Other Embodiment) Next, another embodiment of the present invention will be described.

FIG. 4 is a perspective view of a heat insulating holder according to another embodiment of the present invention.

In this embodiment, the shape of the recess 6 provided in the stay 1 of the fixing device substantially similar to that of the above embodiment is such that the width of the recess is increased as it approaches the end as shown in FIG. By adopting such a configuration, the temperature difference between the inner tip of the depression 6 and the portion without the depression is smaller than that in the case where the depressions having the same width are provided over the entire end portion, and the temperature is smoother over the entire longitudinal direction. It ’s a slope,
This has the advantage that the mechanical strength can be easily secured because the area of the depression can be reduced.

[0030]

As described above, according to the present invention, since the heat insulating effect of the heat insulating holder is enhanced at the end portion, the escape of heat toward the end portion is compensated for, so that the portion of the material to be heated corresponding to the end portion of the heating body is Sufficient heating can be performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heating device according to an embodiment of the present invention.

FIG. 2 is a perspective view of a heat insulation holder used in the heating device according to the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship in the longitudinal direction of the example of the present invention.

FIG. 4 is a perspective view of a heat insulation holder according to another embodiment of the present invention.

FIG. 5 is a diagram showing a temperature distribution in the longitudinal direction.

[Explanation of symbols]

 1 Holder 2 Heating Element 3 Heater Substrate 4 Resistance Heating Element 5 Temperature Detection Element 6 Dimple 7 Fixing Film 8 Pressing Member 9 Pressing Member Core Bar 10 Heat Resistant Elastic Layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoji Tomoyuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Daizo Fukuzawa 3-30-3 Shimomaruko, Ota-ku, Tokyo In Canon Inc. (72) Inventor Shunji Nakamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A heating device comprising: a heating body provided along a direction intersecting with a moving direction of a recording material; and a heat insulating holder for thermally insulating and supporting the heating body along a longitudinal direction. A heating device characterized in that the heat insulation effect is enhanced from the central part to the end part. 2. The heat insulation holder has a U-shaped cross section,
2. The heating device according to claim 1, wherein the end of the heat insulation holder has a recess that forms a space with the heating body. 3. The heating element has a linear resistor that generates heat when energized, and a good heat conductive substrate that supports the resistor and is supported by the heat insulating holder, and the end of the recess is formed. 3. The heating device according to claim 2, wherein the portion is provided inside the substrate end portion and at the same position as or outside the resistor end portion. 4. The apparatus further comprises a film that moves together with the recording material supporting the image, and the image on the recording material is heated by heat from the heating body through the film. The heating device according to claim 1.